1. Field of the Invention
The present invention relates to a current collector, provided with a selector, for a conductor rail, a current collector which comprises a box-shaped frame to which at least three contact fingers have been attached so that they can move, at least two of the fingers at a time being transferrable, by means of a camshaft or a corresponding member, from a retracted position inside the frame to a position protruding from the frame to contact the conductors in the conductor rail.
2. Description of the Prior Art
The term conductor rail denotes a device which distributes electric current and comprises a box-like profile open on one side. Inside the profile there are conductors attached to insulation pieces, the conductors being exposed on a level vertical to the direction indicated by the said opening and the center of the profile so that current can be taken from the conductors through the said opening at an arbitrary point by means of a current collector positioned alongside the rail. Such conductor rails having more than two conductors can be coupled to the network in three phases or they can be coupled so that several coupling circuits are created. When current is received by the current collector from the network in one phase, the object is usually to distribute the load evenly between the various phases. For this reason it is important that the different current collectors can be coupled to the different phases by means of a selector. When the conductor rail is coupled in several coupling circuits it is, of course, important that the current collector, with the help of the selector, can be coupled without difficulty to the correct coupling circuit.
Previously known are current collectors provided with a selector, such as the current collectors according to Finnish published patent applications Nos. 47,236 and 47,237 and that according to German published patent application No. 2,215,451. The former two have a disadvantage in the large size of the current collectors, i.e., the current collectors protrude notably from the conductor rail. In addition, in them it is difficult to direct the contact fingers precisely so that they also contact the conductors properly as described in Finnish published patent application 45,711, a disadvantage which the latter device aims to eliminate. The current collector described in German published patent application No. 2,215,451, on the contrary, retracts almost completely inside the conductor rail. These current collectors provided with a selector have a disadvantage in that they are too easily coupled to any of the current circuits available in the conductor rail. Inadvertently, a layman can easily couple the current collector to a wrong circuit and thereby, for example, load the same phase with all the current collectors.
It is true that a current collector with a separate preselector of the coupling circuit or phase is known from German Pat. No. 2,060,262. This device, however, has a disadvantage in its large size. In the device all the contact fingers are coupled to a contact with the current conductors in the conductor rail. Thereby the creep paths in the current collector in a three-phase system must be dimensioned according to the voltage between the phases (e.g., 380 V). Current conductors in which only the contact fingers in use are in contact with the current collectors can in one-phase operation be dimensioned according to the voltage between the zero conductor and the phase conductor (e.g., 220 V).
The object of the present invention is to eliminate the above disadvantages and provide a current collector which protrudes relatively little from the conductor rail and which also has a coupling circuit preselector.